Immunology is the branch of biomedical science that encloses the study of structure and function of the immune system in all organisms. Immune system plays the most important role in understanding the diseases and also protects us from infections by different types of diffence. Immunology includes all physical, chemical and biological reactions of the organism against the foreign substances. Immune system is divided into two types: innate immunity and adaptive immunity. Adaptive immunity further divided into two types that is humoral and cell mediated immunity.